August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Spatial organization of spontaneous activities in the human visual cortex
Author Affiliations
  • Pinglei Bao
    Neuroscience Graduate Program, University of Southern California
  • Bosco S. Tjan
    Neuroscience Graduate Program, University of Southern California, and Department of Psychology, University of Southern California
Journal of Vision August 2009, Vol.9, 736. doi:10.1167/9.8.736
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      Pinglei Bao, Bosco S. Tjan; Spatial organization of spontaneous activities in the human visual cortex. Journal of Vision 2009;9(8):736. doi: 10.1167/9.8.736.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Spontaneous fluctuations in fMRI BOLD signal have been shown to be temporally correlated across widely distributed brain regions. We investigated the spontaneous fluctuations within the human visual cortex. A standard EPI sequence was used to acquire functional data (3mm isotropic voxels, TR = 1s). Subjects were scanned under a “rest” condition (eyes closed) and four fixation conditions, each consisted of a rotating wedge of high-contrast flickering checkerboard sweeping across one of the four halves of the visual field (upper, lower, left, right) during the entire run. A correlation-weighted cortical labeling method was used to reveal the spatial organization of the temporal coherency. Specifically, we designated a quadrant of V1 (e.g. ventral, left hemisphere) as the reference area, where each voxel was given a numeric label - either the eccentricity value or the polar angle from a separate retinotopy experiment. For a given voxel elsewhere on the cortex, we computed the temporal correlation between its spontaneous activities with those of each voxel in the reference area. The squared correlation coefficients were then combined with the reference labels to obtain a correlation-weighted label for the voxel in question. When eccentricity values were used as reference labels, the maps of correlation-weighted labels resembled eccentricity maps in all quadrants of all visual areas studied (V1, V2, V3) in the “rest” condition, across both horizontal and vertical meridians. The same was observed in the un-stimulated quadrants in the fixation conditions. Correlation-weighted labels continued to show a ring-like structure even when the reference region was stimulated by the rotating wedge or when polar angles were used as reference labels, suggesting that the correlations between spontaneous activities are strongly organized by eccentricity but remain non-specific in other spatial directions. This robust eccentricity organization of the spontaneous activities may reflect a fundamental organizational principle of the visual system.

Bao, P. Tjan, B. S. (2009). Spatial organization of spontaneous activities in the human visual cortex [Abstract]. Journal of Vision, 9(8):736, 736a, http://journalofvision.org/9/8/736/, doi:10.1167/9.8.736. [CrossRef]
Footnotes
 Support: NIH grant EY016391.
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